Robot Room Copper Connection
Excellent, easy-to-use free PCB layout software for home use.
Other editions include the ability to export to Gerber or save the PCB files as open text format.
So, unlike other free PCB software, you aren't locked into a specific PCB manufacturer or product.
Perfect for hobbyists, students, and professional designers.

Electric Motors, Gearmotors, Gearheads, and Encoders

Maxon
High-quality miniature DC motors. The cost of brand new motors are out of the price range of most hobbyists.
So, use this site to look up the motor specifications that are listed on eBay.

Faulhaber
Makers of fine quality gearmotors with company names of “MicroMo”, “Mini-Motor”, and “Faulhaber”.

Portescap
Another manufacturer of excellent small motors. Sometimes the name is shortened to “escap”.

Magazines and Books for Robots, Software, Machining, and DIY

Make
Instructions and tutorials on making a wide variety of things. Always something new!